Take Smooth Shading into account with Normals Bake
You can use the bake selected to active feature.


Duplicate your object.
Set one copy to smooth, and the other to sharp.
Add a UV map and image to the sharp one.
Select the smooth one first, then the sharp one (so the sharp one is active).
Enable Selected to active in the bake settings.
Set Bake Mode to Normals.
Press Bake!


You can also use this trick to add bevelled edges for low-poly models. Just add a bevel modifier to the "smooth" object.